How do you compare the freezing points of water and brine using physical experiments?

Put a glass of brine in the refrigerator, wait until the water is about to solidify, take out the brine and observe the water solidification process.

One. Verify that the freezing point of salt water and sugar water is lower than that of water:

The addition of sugar and salt will reduce the freezing point of water.

1.You can adjust the freezer of the refrigerator at home to 0 degrees, and then put pure water, sugar water, and salt water in it at the same time.

2.After a while, you can observe to see if the liquid solidifies.

3.It was concluded that salt water and sugar water have a lower freezing point than water.

Two. Verify that the freezing point of sugar water is lower than that of brine:

1.One cup of the same amount of sugar water and one cup of salt water (the same amount of sugar and salt in the water)2. At the same time, put it in the freezer compartment of the refrigerator.

3。Observe the condensation of two glasses of water at regular intervals.

4。Conclusion: The freezing point of brine is lower.

In general, a homogeneous mixture of several substances has a lower melting point than any one component and a higher boiling point than any one component. Brine is a homogeneous mixture (solution) of salt and water, which can reach -21 at the lowest melting point and freeze when the temperature is lower than -21, so it can also melt ice and snow with salt water.

Refrigerator with transparent doors. Three beakers. Water. Salt. Thermometer.

Put the same water in a beaker, different salts, insert a thermometer, put it in the refrigerator, and record the temperature.

Pretty much. Take the same quality of water, and salt water, put it in the same beaker, and then put it in the same environment. Slowly lower the temperature and see which one freezes first.

Well, it's better to use chemistry to see which one is easier to boil, and the freezing point that is easier to boil is lower.

Salt waterFreezing pointLower than pure water is because the solute is dissolved in water to form a solution, the freezing point decreases, and the boiling point increases. Here's how it works:

Salt molecules and water molecules in brine.

The presence of salt molecules in the brine mixture can interfere with the water molecule noise or sail row, resulting in a lower freezing point of the brine. According to this principle, the snowfall is salted to speed up the snow melt.

Desalinated water and pure water are two different terms theoretically and conceptually, but sometimes in practical engineering, desalinated water is called pure water, because the desalination group water judgment station is mainly in the petrochemical industry.

It is called so in the design institute, but pure water is general water that has undergone reverse osmosis, and it can be called deionized water.

It can also be called pure water, if by definition, hail is very different, but if it is said in practice, it cannot be called wrong.

For example, petrochemical plants will have water purification stations, desalination stations, circulating water stations, etc., but photovoltaic or fertilizer plants will be called chemical water workshops and ultrapure water stations.

The solidification and ambush point of brine is lower than that of pure water because the solute is dissolved in water and the solution is formed, the freezing point decreases and the boiling point increases. Here's how it works:

The size and nature of salt molecules in brine are different from those of water, and the presence of salt molecules in the brine mixture will interfere with the arrangement of water molecules, resulting in a decrease in the freezing point of brine. According to this principle, the snowfall is salted to speed up the snow melt.

The freezing point of pure water is 0 degrees, while the freezing point of salt water is below 0 degrees.

You can find a comparison table of the freezing point of different concentrations of salt water on the Internet, remember that the freezing point of 15% salt water is good for the town of Tong elephant in Akeno around -20 degrees.

Highways often use salt water to dissolve snow in winter.

From the microscopic point of view of molecules, when the concentration of the solution is low, it is very difficult for the molecules to form a directional regular arrangement, and the factors affected by the removal of solute are very large, and it takes a lot of energy to solidify, so the freezing point is high. When the concentration of the solution increases, the content of the solute increases, the influence of the solvent on the solute becomes relatively small, and the molecules are easier to form a regular arrangement, so it is easier to crystallize, so the freezing point is reduced.

In layman's terms, the solution is actually equivalent to the impurities in the liquid, and the dilute solution is mainly solvent properties, and the more impurities, the less easy it is to unite and the lower the freezing point.

In terms of physical explanation, it needs to be explained by the dependence of the dilute solution.

The doping of solutes reduces the vapor pressure of the original solvent. The freezing point of the solution is the temperature at which the solvent crystals begin to be precipitated from the solution, and the system is composed of the solution (liquid phase), the solvent solid phase and the solvent vapor phase. Taking aqueous solutions as an example, for aqueous solutions, the solvent solid phase is pure ice.

Due to the decrease in the vapor pressure of the solution, when k(0), the vapor pressure of the ice is still there, and the vapor pressure of the solution must be lower, so that the solution and the ice can not coexist, only at a certain temperature below k, the vapor pressure of the solution can be equal to the vapor pressure of the ice, and the temperature at this time is the freezing point of the solution, so the freezing point of the solution is always lower than that of the pure solvent. The greater the concentration of the solution, the more the vapor pressure drops, and the more the freezing point drops.

The freezing point, specific gravity, specific heat and other physical properties of brine change with the concentration of brine. The freezing point of the brine solution decreases with the increase of salt concentration, until it decreases to the ice salt crystallization point, which is equivalent to the temperature when the whole solution is frozen into a whole ice salt crystal, which is the lowest freezing point, and the concentration exceeds this point, but the freezing point rises.

The minimum temperature of the brine is 20 degrees Celsius, and the freezing point of the brine depends on the concentration of the brine. No matter what kind of brine, when the concentration of brine is less than a certain value, its solidification temperature decreases with the increase of concentration, and when the concentration is greater than this fixed value, the solidification temperature increases with the increase of concentration.

When there is dust or dirt in the home, splash some salt water on the dirty area to achieve the effect of sterilization, the principle is to use the osmotic pressure of the salt water to make the bacteria lose moisture. In addition, if you sprinkle some salt water in the corner during the cleaning of the house, you can also avoid the invasion of cockroaches and other mosquitoes. In this way, you can also avoid buying pesticides, and it seems to have the effect of preventing global warming.

Salt water condensation point?

The problem is too specific, the salt water concentration will affect its freezing point, you just need to know that it is below 0 degrees.

The concentration is large and the freezing point is low.

The brine decreases and takes the vapor pressure of the water, so that the freezing point of the brine decreases and the boiling point rises, and it can be quantitatively calculated.

For details, you can refer to the dependence of dilute solution non-electrolyte megaming, find an inorganic chemistry book, which should have a guess.

The freezing point of brine is lower than that of pure water, which is a solution formed by the solute dissolved in water, and the freezing point decreases and the boiling point increases. Here's how it works:

The size and nature of salt molecules in the brine are different from those of water, and the presence of salt molecules in the brine mixture will interfere with the arrangement of water molecules, resulting in a decrease in the freezing point of the brine. According to this principle, the snowfall is salted to speed up the snow melt.

Summary. Be clear - take two identical cups and put the same amount of brine and water at a similar temperature, but if the ice melts, how can you prove that the brine has a lower freezing point? It is recommended to put the method into the refrigerator for the test, other variables must be controlled, at the same time the research object is salt water and water, do not take ice cubes and salt to do this experiment, because if the ice does not melt, it is impossible to form brine with salt, the design must pay attention to the study of the freezing point problem physical experiment pays attention to the control variable idea, at the same time put it in the refrigerator freezer, after 1 hour of observation, the surface of the cup with water forms ice, and there is no coagulation phenomenon at the edge of the salt water.

Be clear - take two identical cups and put the same amount of brine and water at a similar temperature, but if the ice melts, how can you prove that the brine has a lower freezing point? It is recommended to use the method of putting it in the refrigerator for testing, other variables must be controlled, and the research object is to take a branch of salt water and water, do not take the ice bureau and salt to do this experiment, because if the ice is not melted, it is impossible to form brine with salt, and the design must pay attention to the study of the freezing point problem of the physical experiment pays attention to the idea of control variables, and at the same time put it in the freezer compartment of the refrigerator, after 1 hour of observation, the surface of the cup of water forms an ice layer, and Tong Min lifts the salt water without any coagulation phenomenon.

Take two identical cups of Fengfan Blind Yinkong, put the same amount of salt water and water with similar temperatures, and put them in the freezer compartment of the refrigerator at the same time, and wait for 1 hour to observe, the surface of the cup with water forms an ice layer, and there is no agglutination on the edge of the salt water, which proves that the agglutination point of the salt water is lower.

It is not the same through life experience, and the freezing of the ground on snowy days is to sprinkle salt in order to reduce the freezing point.

To determine whether the freezing points of sugar water, brine and pure water are the same, it is necessary to measure the freezing points of these three substances But the measurement of freezing point is relatively inconvenient, so it is possible to measure the melting point of these three substances according to the same freezing point and melting point of the same substance, and design this experimental process with reference to the melting experiment in the textbook Answer: Answer: (1) Take three small plastic cups and fill them with pure water, salt water and sugar water of the same quality respectively, and then put them in the refrigerator to freeze

2) After they are all frozen, take them out and break them separately, and then put them in three small beakers (3) Use a thermometer to measure the temperature at each moment in the melting process (4) From the experimental data, the respective melting points of pure water, salt water and sugar water can be obtained, and conclusions can be drawn Comments: The topic of the design experiment has always been a headache for students, in fact, the topic of the design experiment is basically the experiment learned in the textbook, and it is necessary to pay attention to the experiment learned in the textbook, and then give the conditions according to the topic.

This is Henry's Law of physical chemistry in college, right?

Explain with the knowledge of the second year of junior high school, click, it's a little more difficult.

The freezing point is the temperature at which the vapor pressure of the solid phase of a substance and the vapor pressure of its liquid phase is equal to that of its liquid phase. The freezing point of pure water, also known as the freezing point, is 273 kAt this temperature, the vapor pressure of water and ice is equal.

However, at 273K, the vapor pressure of the aqueous solution is lower than that of pure water, so the aqueous solution does not freeze at 273K. The temperature continues to drop because the vapor pressure of ice drops more than that of aqueous solution, and when it drops to Tf, the vapor pressure of the ice and the solution is equal, and Tf is the freezing point of the solution. The freezing point of a solution is always lower than that of a pure solvent.

This phenomenon is called a decrease in the freezing point of the solution. As with the increase in the boiling point, the freezing point of the solution decreases in δTF and is proportional to δp, so the decrease in the freezing point of the dilute solution of the non-electrolyte is proportional to the mass molar concentration of the solution, but not to the nature of the solute. Namely:

tf=kf bb"

The above is the explanation of physical chemistry.

To put it bluntly, there are salt ions in the water, so a part of the water on the surface is taken up by salt. This results in a drop in the vapor pressure of the water. Whereas, the vapor pressure of ice is constant.

The vapor pressure of the ice at the freezing point is less than or equal to the vapor pressure of the water, so after adding salt, the vapor pressure of the water becomes smaller, and the vapor pressure that is equal to the original becomes the ice larger. At this time, because the vapor pressure of the ice drops rapidly, it is necessary to lower the temperature so that the vapor pressure of the ice is equal to the vapor pressure of the ice. This results in a lower freezing point.